Method for correcting imbalance errors in a direct conversion receiver
a direct conversion and imbalance correction technology, applied in the field of direct conversion receivers, can solve the problems of audible distortion, difficult to build training sequences, and significant software and hardware modifications, and achieve the effects of reducing the number of errors, and improving the accuracy of correction
Active Publication Date: 2013-12-17
MOTOROLA SOLUTIONS INC
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Benefits of technology
The present patent relates to a method for correcting imbalance errors in a direct conversion receiver used in a communication system. The method does not require any training sequences, preamble signals, or HOS technique, and can be implemented on an embedded platform. The method uses a two-parameter adaptive system to estimate and correct the amplitude and phase imbalance errors between the baseband I and Q signal components. The method can be used in a direct conversion receiver without causing any audible distortion or degrading the reception performance of the receiver.
Problems solved by technology
However, due to temperature dependencies and production imperfections in the direct conversion receiver, the phase difference between the baseband I and Q signal components may not be exactly 90 degrees causing an amplitude and phase imbalance to occur between the baseband I and Q signal components.
This amplitude and phase imbalance between the baseband I and Q signal components degrades the reception performance of the direct conversion receiver resulting in audible distortion.
However, the existing methods make use of either training signals / tone or preamble signal, and such training sequences are difficult to build requiring significant software and hardware modifications.
In fact, two way radios that support analog mode do not use preamble signals making it very difficult to estimate and correct the amplitude and phase imbalance errors.
The HOS technique makes assumptions about the signal sources thus making it unsuitable for constant envelope FM based 2-way radio.
Moreover, HOS techniques are computationally intensive making it infeasible for implementation on an embedded platform.
However, from a practical standpoint, it is not possible to have the I signal component xI(t) and the Q signal component xQ(t) of the complex input signal x(t) that are amplitude and phase imbalance free.
The amplitude and / or phase imbalance results in the generation of audio distortion that can be easily heard by the human ear.
Further, the amplitude and / or phase imbalance can result in an increased carrier falsing which can adversely affect the overall performance of the direct conversion receiver 100.
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[0013]A communication system comprises a direct conversion receiver for correcting imbalance errors. The direct conversion receiver receives a radio frequency (RF) signal and converts the RF signal to baseband signals. The direct conversion receiver further translates the baseband signals to digital signals having a direct current (DC) offset and applies a DC offset correction to the digital signals having the DC offset to generate first DC offset corrected signals. An imbalance correction unit of the direct conversion receiver then applies an imbalance correction to the first DC offset corrected signals by estimating an error between an average envelope of the first DC offset corrected signals and an average envelope of second DC offset corrected signals. The imbalance correction unit is fixed at initial imbalance parameter values. The envelope of the second DC offset corrected signals at the output of the imbalance correction unit depends on the initial imbalance parameter values....
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A communication system comprises a direct conversion receiver for correcting imbalance errors. The direct conversion receiver receives a radio frequency (RF) signal and converts the RF signal to baseband signals. The direct conversion receiver further translates the baseband signals to digital signals having a direct current (DC) offset and applies a DC offset correction to the digital signals having the DC offset to generate first DC offset corrected signals. An imbalance correction unit of the direct conversion receiver applies an imbalance correction to the first DC offset corrected signals by estimating an error between an average envelope of the first DC offset corrected signals and an average envelope of second DC offset corrected signals. The imbalance correction unit is fixed at initial imbalance parameter values. The direct conversion receiver further updates the initial imbalance parameter values of the imbalance correction unit based on the estimated error for correcting imbalance errors.
Description
FIELD OF THE DISCLOSURE[0001]The present disclosure relates generally to a direct conversion receiver in a communication system and more particularly to a method for correcting imbalance errors in the direct conversion receiver operating in the communication system.BACKGROUND[0002]In modern mobile communications, direct conversion receivers are widely used for wireless communications due to their lower complexity and lower power consumption. In a direct conversion receiver, a received radio frequency signal is down-converted to baseband In-phase (I) and Quadrature-phase (Q) signal components to estimate the phase and amplitude of the received radio frequency signal. In an ideal case, the phase difference between the baseband I and Q signal components should be 90 degrees in order to correctly estimate the phase and amplitude of the received radio frequency signal. However, due to temperature dependencies and production imperfections in the direct conversion receiver, the phase diffe...
Claims
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IPC IPC(8): H03D1/04
CPCH04B1/30
InventorRAO, YADUNANDANA N.LAMPERT, CHET A.
OwnerMOTOROLA SOLUTIONS INC